/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 * 
 *      http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.catalina.core;

import org.apache.catalina.*;
import org.apache.catalina.connector.Connector;
import org.apache.coyote.ProtocolHandler;
import org.apache.juli.logging.Log;
import org.apache.juli.logging.LogFactory;
import org.apache.tomcat.util.res.StringManager;
import org.apache.tomcat.util.threads.ThreadPoolExecutor;

import java.util.concurrent.Executor;

/**
 * <p>
 * A {@link LifecycleListener} that triggers the renewal of threads in Executor
 * pools when a {@link Context} is being stopped to avoid thread-local related
 * memory leaks.
 * </p>
 * <p>
 * Note : active threads will be renewed one by one when they come back to the
 * pool after executing their task, see
 * {@link org.apache.tomcat.util.threads.ThreadPoolExecutor}.afterExecute().
 * </p>
 * <p>
 * This listener must be declared in server.xml to be active.
 */
public class ThreadLocalLeakPreventionListener implements LifecycleListener,
		ContainerListener {

	/**
	 * The string manager for this package.
	 */
	protected static final StringManager sm =
			StringManager.getManager(Constants.Package);
	private static final Log log =
			LogFactory.getLog(ThreadLocalLeakPreventionListener.class);
	private volatile boolean serverStopping = false;

	/**
	 * Listens for {@link LifecycleEvent} for the start of the {@link Server} to
	 * initialize itself and then for after_stop events of each {@link Context}.
	 */
	@Override
	public void lifecycleEvent(LifecycleEvent event) {
		try {
			Lifecycle lifecycle = event.getLifecycle();
			if (Lifecycle.AFTER_START_EVENT.equals(event.getType()) &&
					lifecycle instanceof Server) {
				// when the server starts, we register ourself as listener for
				// all context
				// as well as container event listener so that we know when new
				// Context are deployed
				Server server = (Server) lifecycle;
				registerListenersForServer(server);
			}

			if (Lifecycle.BEFORE_STOP_EVENT.equals(event.getType()) &&
					lifecycle instanceof Server) {
				// Server is shutting down, so thread pools will be shut down so
				// there is no need to clean the threads
				serverStopping = true;
			}

			if (Lifecycle.AFTER_STOP_EVENT.equals(event.getType()) &&
					lifecycle instanceof Context) {
				stopIdleThreads((Context) lifecycle);
			}
		} catch (Exception e) {
			String msg =
					sm.getString(
							"threadLocalLeakPreventionListener.lifecycleEvent.error",
							event);
			log.error(msg, e);
		}
	}

	@Override
	public void containerEvent(ContainerEvent event) {
		try {
			String type = event.getType();
			if (Container.ADD_CHILD_EVENT.equals(type)) {
				processContainerAddChild(event.getContainer(),
						(Container) event.getData());
			} else if (Container.REMOVE_CHILD_EVENT.equals(type)) {
				processContainerRemoveChild(event.getContainer(),
						(Container) event.getData());
			}
		} catch (Exception e) {
			String msg =
					sm.getString(
							"threadLocalLeakPreventionListener.containerEvent.error",
							event);
			log.error(msg, e);
		}

	}

	private void registerListenersForServer(Server server) {
		for (Service service : server.findServices()) {
			Engine engine = (Engine) service.getContainer();
			engine.addContainerListener(this);
			registerListenersForEngine(engine);
		}

	}

	private void registerListenersForEngine(Engine engine) {
		for (Container hostContainer : engine.findChildren()) {
			Host host = (Host) hostContainer;
			host.addContainerListener(this);
			registerListenersForHost(host);
		}
	}

	private void registerListenersForHost(Host host) {
		for (Container contextContainer : host.findChildren()) {
			Context context = (Context) contextContainer;
			registerContextListener(context);
		}
	}

	private void registerContextListener(Context context) {
		context.addLifecycleListener(this);
	}

	protected void processContainerAddChild(Container parent, Container child) {
		if (log.isDebugEnabled())
			log.debug("Process addChild[parent=" + parent + ",child=" + child +
					"]");

		if (child instanceof Context) {
			registerContextListener((Context) child);
		} else if (child instanceof Engine) {
			registerListenersForEngine((Engine) child);
		} else if (child instanceof Host) {
			registerListenersForHost((Host) child);
		}

	}

	protected void processContainerRemoveChild(Container parent,
	                                           Container child) {

		if (log.isDebugEnabled())
			log.debug("Process removeChild[parent=" + parent + ",child=" +
					child + "]");

		if (child instanceof Context) {
			Context context = (Context) child;
			context.removeLifecycleListener(this);
		} else if (child instanceof Host || child instanceof Engine) {
			child.removeContainerListener(this);
		}
	}

	/**
	 * Updates each ThreadPoolExecutor with the current time, which is the time
	 * when a context is being stopped.
	 *
	 * @param context the context being stopped, used to discover all the Connectors
	 *                of its parent Service.
	 */
	private void stopIdleThreads(Context context) {
		if (serverStopping) return;

		if (!(context instanceof StandardContext) ||
				!((StandardContext) context).getRenewThreadsWhenStoppingContext()) {
			log.debug("Not renewing threads when the context is stopping. "
					+ "It is not configured to do it.");
			return;
		}

		Engine engine = (Engine) context.getParent().getParent();
		Service service = engine.getService();
		Connector[] connectors = service.findConnectors();
		if (connectors != null) {
			for (Connector connector : connectors) {
				ProtocolHandler handler = connector.getProtocolHandler();
				Executor executor = null;
				if (handler != null) {
					executor = handler.getExecutor();
				}

				if (executor instanceof ThreadPoolExecutor) {
					ThreadPoolExecutor threadPoolExecutor =
							(ThreadPoolExecutor) executor;
					threadPoolExecutor.contextStopping();
				} else if (executor instanceof StandardThreadExecutor) {
					StandardThreadExecutor stdThreadExecutor =
							(StandardThreadExecutor) executor;
					stdThreadExecutor.contextStopping();
				}

			}
		}
	}
}
